5-Aryl-2-methylisoxazolidin-3-yl-3-phosphonates have been synthesised from N-methyl-C-diethoxyphosphorylnitrone and vinyl aryls in good yields. Isoxazolidine phosphonates obtained herein were evaluated for activity against a broad range of DNA and RNA viruses. None of the compounds were endowed with antiviral activity nor cytostatic activity at 100 to 250 μM concentrations.